The present invention relates to a shaft for use in a machine to perform at least one operation. In particular, it relates to a lightweight, low cost, hollow shaft having a hollow, tubular, shell like portion containing a hardened, moldable material within its core.
Cross reference is made to the following application filed concurrently herewith: U.S. application Ser. No. 09/293,098 entitled "Plastic Shafts with Molded Core and External Feature" by Robert D. Russell.
While the present invention has utility in apparatus comprising various mechanical components, it has particular application and will henceforth be described with reference to electrostatographic reproducing apparatus. Briefly, and as illustrated in FIGS. 1 and 2, in electrostatographic printing apparatus commonly in use today a photoconductive insulating surface 10 which is typically the surface of a rotatably drum is charged to a uniform potential by a charge corotron 12 and thereafter exposed to a light image of an original document 15 to be reproduced on an exposure platen 16 by means of exposure lamp 17, the exposure discharging the photoconductive insulating surface in exposed or background areas creating an electrostatic latent image on the photoconductive insulating surface of the document. A developer unit 20 is which corresponds to the image areas contained within the apparatus and has developer material to developed the electrostatic latent image. Typically, the developer material has charged carrier particles and charged toner particles which triboelectrically adhere to the carrier particles and during development, the toner particles are attracted from the carrier particles to the charged areas of the photoconductive insulating surface. The developed image on the photoconductive insulating layer is subsequently transferred at a transfer station 24 to a support surface, such as copy paper, which is fed by feeder 22 to provide intimate transfer contact between the insulating area and the copy paper. The toner image on the copy paper is subsequently, permanently affixed on the copy paper by the application of heat and/or pressure in a fuser 23. Subsequent to the transfer of the toner image to the support surface, any residual toner remaining on the photoconductor is cleaned by a cleaner 19 in preparation for the next imaging cycle. FIG. 2 illustrates the claim shell nature of this machine having a lower frame member 25 and an upper frame member 26 which has two shafts, 27, 28 in the copy sheet transport system. For example, the shafts 27 and 28 may be paper path nip shafts.
Alternatively, the electrostatic latent image may be generated from information electronically stored or generated in digital form which afterwards may be converted to alphanumeric images by image generation, electronics and optics. For further information on such apparatus, attention is directed to U.S. Pat. No. 4,372,668 to Malachowski et al., and U.S. Pat. No. 4,660,963 to Stemmle et al.
In these machines, shafts are typically used to provide a variety of features performing functions within the machines. For example, shafts typically have gears, rolls, pulleys or other drive mechanisms mounted thereon to enable driving various parts or systems in the machine. For example, the shafts may be paper path nip shafts. In addition, the shafts may have retention or location features such as, snaps, fitting elements or stops or may contain other features such as bearings, bushings, rollers, journals and O-rings. Initially, the shafts were typically made from solid materials such as, metals like, steel and aluminum, and the individual functional features or elements such as rollers or gears were individually mounted to the shaft and secured thereto. Typically, this assembly process was manually completed as it did not readily lend itself to automated assembly. While satisfactory in many respects, such shaft assemblies were both heavy and costly in that solid shafts contained more metal and therefore cost more. Each of the individual functional features has to be separately manufactured, separately assembled onto the shaft assembly, all of which increased both materials and assembly time and cost particularly when most of the functional features had to also be located and fixed by way of set screws or other such device to the shaft. Alternatively, the functional features have been formed on metal stock material by such conventional metal working techniques as turning, milling and grinding. In addition, the weight of such shaft assemblies provided a high moment of inertia which necessitated increased drive power requirements.
Referring now to FIGS. 5 and 6, a shaft assembly 7 is shown for use in guiding paper sheets through a copy or printing machine. The shaft assembly 7 is manufactured by first providing a 8 millimeter stainless steel shaft 2 having a generally cylindrical shape and including grooves 5 for placement of E-rings to secure the shaft assembly 7 within the printing machine. Knurls 3 are machined into the periphery 4 of the shaft 2. Rollers 8 are fitted onto the shaft 2 at the knurls 3 by pressing the hollow rollers 8 onto the shaft 2. This prior art shaft assembly is both heavy and expensive. The use of a solid steel shaft adds significant weight to the shaft assembly and the machining requirement of the knurls as well as the assembly time to assemble the rollers 8 to the shaft 2 adds manufacturing and assembly costs to the shaft assembly 7.
Attempts have been made to provide shaft assemblies with reduced weight and manufacturable at a lower cost. One such attempt is the use of a two-component or composite shaft process. The composite shaft process may be more fully understood with reference to U.S. Pat. Nos. 5,439,916, 5,876,288, and 5,683,641, all to Jaskowiak and assigned to the same assignee as the present invention. The composite shaft process utilizes a hollow metal tube to which slits or holes are machined through the wall of the tube. The tube is placed in a molding machine and hard moldable material is injected into the opening on the end of the tube and permitted pass through the apertures in the periphery of the tube to fill functional features formed in a mold cavity. While the composite shaft process provides for improved performance and reduce costs, the use of a cylindrical metal tube adds costs to the shaft assembly and the requirement of machining the apertures in the periphery of the tube further adds costs to the process. Further, the design of the composite shaft is limited by the fact that the tube is typically cylindrical with a generally uniform outer periphery.
The present invention is directed to alleviate at least some of the aforementioned problems.
The following disclosures may be relevant to various aspects of the present invention: